How Does Soundproofing Work

Are you considering soundproofing your house? Want to learn more about it and understand how does soundproofing work and the science behind sound insulation?

Let’s face it; sometimes, there’s just too much noise around us. Noisy neighbors upstairs, loud music next door, or even sounds from the outside might be disturbing your peace. 

And you’re right in trying to do something about it. 

Now, soundproofing, or sound insulation, as the technique is also called, is one of the most effective ways to block sound waves from entering your home. 

But before you start researching different soundproofing materials and methods, it’s good to understand how soundproofing works, in general, and that’s what this page is all about. 

Below, you’ll find information on how sound works and the different soundproofing methods to stop the sound from traveling through walls, floors, and ceilings.

We have a lot to cover, so let’s get right to it, shall we?

What is Soundproofing?

A quick note – To learn the basics of soundproofing, check out my full explanation of what soundproofing is and also what it is not.

Soundproofing is a process of blocking or reducing unwanted sounds or background noises from either entering your house or being heard outside of it. 

In practical terms, this means using various materials and techniques to increase sound isolation and increase mass to reduce sound vibration. 

Now, I have to be upfront about this – Many sounds cannot be fully eliminated. It’s impossible, at least not without serious structural and construction work, to soundproof a room so no sound can enter from outside. 

However, you can reduce noises and sounds significantly enough so that they either become bearable or you no longer notice them at all. 

And that’s the goal of soundproofing. Here’s how you achieve it. 

How Does Soundproofing Work – The Science Behind Sound Insulation

To understand how soundproofing works, we have to start by discussing the science of sound. 

Only when you understand how sound works and how sound waves travel can you comprehend the different strategies to either stop or absorb it. 

So, what is sound? Well, in the simplest terms, the sound is energy. Sounds are produced when things vibrate. That vibration is then pushed outward, away from its source. The sound energy travels by making either the air or objects around it vibrate too (this is hugely important to remember, as you’ll see shortly.)

The process continues until this energy (or vibration) reaches our ears. 

Another important thing to understand is how sound travels.

Remember, just a couple of lines above, I mentioned that sound energy makes air and objects vibrate. But it doesn’t happen at the same time. This means that some sounds travel by making the air vibrate, and some because objects vibrate. We refer to those sounds as either airborne or impact. 

Airborne sounds are created when the sound energy travels through the air. This is what happens when you speak, for instance. The sound of your voice makes the air vibrate, and that’s how your words reach the other person. TV, radio, music playing from speakers are other examples of airborne sounds. 

These sounds, typically, enter your house through vents, open spaces, cracks, doors, even electrical outlets. In short, if air can get in somehow, an airborne sound will also get that way.

Take a look at this room. 

You can immediately see several places through which airborne sounds can be heard:

• Gaps in old window frames
• Window lock
• Gaps under windowsills
• Chimney
• Crack in the wall above the mirror
• Electrical outlets
• Ceiling lamp, and more.

Impact sounds, on the other hand, happen because the sound makes objects vibrate. So, you hear footsteps because the floor vibrates as you walk. You hear someone hammering a nail into a wall next door because the sound of their hammer hitting the nail makes the wall vibrate, and so on.

Impact noises are the most common sounds that travel through walls, ceilings, and floors. 

Because these two types of sounds work differently, they also enter your house in different ways. 

Soundproofing works by either reducing or absorbing the sound along the exact way it enters your house. 

In the case of airborne noise, for example, you soundproof the house by closing cracks, gaps in walls, drafts in windows, and so on. That’s because air can get into the room through them. And since these sounds are carried by air, they can enter the house that way too. 

For impact noises, you use methods like sound dampening to reduce the impact of the vibration. To do this, you place various dampening materials between various structural elements of the building – between sheetrock and framing, for example – to stop impact sound energy from being transmitted.

Different Methods of Soundproofing

Because we’re dealing with different types of sounds, we also use different methods to block, reduce, or absorb them. 

In fact, there are four methods to soundproof a house.

#1. Blocking all entry points for airborne sound to prevent noise from leaking in or out

The most basic way to reduce the impact of airborne noise is by sealing and soundproofing all of its entry points. In practical terms, this means sealing all openings in walls, ceilings, floors, doors, windows, etc. 

Various products like acoustical sealants, door seals, acoustical window inserts, and more help close those sound leaks. 

#2. Damping parts of the structure so that less sound energy travels through it

A major part of noise pollution in houses, apartments, or offices is that the sound also travels through solid materials – walls, floors, ceilings. 

What’s more, it often comes out on the other end with a similar intensity and volume. 

You eliminate that problem by placing sound damping materials along the path of soundwaves traveling through the structure. 

Let’s use a wall between two rooms as an example. The chances are that the wall has a multilayered structure. There’s sheetrock on one end, the wall frame in the middle, and another layer of sheetrock in the next room. 

Sound can make each of the layers vibrate with the same intensity, meaning that the sound can enter the next room at a similar level as at its source. 

Damping materials reduce the intensity of sound. It may still enter the room, of course. However, those materials will greatly reduce the sound’s volume, often to a point where you either don’t notice it anymore or are not disturbed by it. 

Some of the techniques used to damp these noises include:

• Installing sound-absorbing materials like RSIC clips, rubber stud isolators, floor underlayment, or elastomeric sheetrock glue (also known as green glue) to help dampen noise transmission.
• Adding acoustic foam, panels, soundproof foam, or mass-loaded vinyl to add noise-reducing mass to the structure.

This image shows just some of the places where you could add damping materials and reduce the impact of sound transmitted through walls. 

#3. Increasing structural mass

Finally, you can also reduce the amount of vibration by creating a denser structure in your walls, ceilings, and so on.

In this case, your goal is to place an obstacle that will reduce the energy transmitted with the vibration. 

Unfortunately, this method works for new builds, specifically. It requires you to change or adjust the structure of the wall, ceiling, or floor. 

For example, one of the most effective ways to increase the structural mass is by adding double-layered sheetrock to walls. You can also increase the thickness of wall framing, and overall, use heavier and denser building materials. 

#4. De-coupling one structure from another

Finally, you can also de-couple or separate one side of the structure from another. As a result, each of those sides will vibrate independently. And because of that, any transmission of structure-borne sound between them will be impossible.

Again, this is quite a complex method, often involving constructing what we call a room within a room. 

Some ways to do that include using double-stud walls or staggered stud walls and implementing resilient sound insulation clips and hat channels.

And that’s it…

Now you know how soundproofing works. The next thing to learn is how well it works and what sounds you can reduce or eliminate with it.